Poly(lactic acid)-poly(ethylene oxide) block copolymers: new directions in self-assembly and biomedical applications.

In this review, we focus on recent developments in biomaterials of poly(lactic acid)-poly(ethylene oxide)-poly(lactic acid) (PLA-PEO-PLA) triblock copolymers. This system has been widely explored for a number of applications in controlled and sustained release of drugs and in tissue engineering devices. New insights into self-assembly of these materials have resulted in new PLA-PEOPLA solutions and gels with novel structural, mechanical, and drug release properties. Recent innovations include hydrogels with nanoscale crystalline domains, solutions and gels based on PLA stereocomplexes, and nanoparticle-copolymer assemblies. We first briefly review synthetic approaches to these materials. We then describe characterization of the solution properties, formation of micelles, drug release characteristics, and investigation of the sol-gel transition. The properties of PLA-PEO-PLA hydrogels are then discussed, including the effect of crystalline domains on the gel microstructure and efforts to tune the elastic modulus and degredation properties of gels through the addition of chemical crosslinks. In the second half of the review, we discuss the wide variety of biomedical applications currently being pursued for PLA-PEO-PLA triblock copolymer systems. Polymer-nanoparticle complexes have been investigated to facilitate the formation of metal nanoclusters used as biosensors, as well as to enhance the elastic modulus of hydrogels. Thin polymer films have also been investigated for use as tissue engineering scaffolds and as drug-eluding coatings for stents and other medical implants. Finally, we discuss future directions for biomedical applications of this system, including new strategies for improving the specificity and cell affinity of PLA-based biomaterials.

Customized gold weight eyelid implantation in paralytic lagophthalmos.

UNLABELLED: Gold eyelid implantation is widely considered the procedure of choice to reanimate the upper eyelid in paralytic lagophthalmos. Commercially supplied implants are not readily available in all places and are sometimes cumbersome to import. OBJECTIVE: We aimed to devise a method whereby every surgeon performing gold eyelid implantation could have easy and quick access to the implant. Furthermore, we aimed to develop a means of creating an implant of the exact weight required for complete eyelid closure. STUDY DESIGN AND SETTING: A prospective study was performed from 1997 to 2005 in a tertiary research hospital, involving 50 subjects requiring gold upper eyelid implantation and using the technique in question. RESULTS: Only patients with a minimum follow up of one year were included in the study group. Symptoms improved in 96 per cent of subjects, who were able to dispense with eyedrops and eye ointments. Visual acuity improved in 92 per cent of patients. There were two extrusions amongst the early cases. CONCLUSION AND SIGNIFICANCE: Customized gold eyelid implantation offers an alternative in regions where commercial implants are not easily obtained.